Field of the Invention
The invention relates to a method for transmitting a digital information signal in the form of a plurality of a sequences of information symbols, each symbol having a uniform bit length and each such sequence of symbols occurring in a respective input channel, check words being included in the transmitted signal as a result of encoding to enable correction of erroneous symbols caused by said transmitting, the method includes:
applying a first block of s symbols, one from each such input channel, in a first arranging state to a first error correcting encoder to generate p first check symbols. Additionally each symbol is delayed in said first block and each of the p first check symbols by a respective different delay time to provide a resulting second block of symbols in a second arranging state. The second block of symbols is applied to a second error correcting encoder to generate a q second check symbols, and the information symbols as well as the first and second check symbols are transmitted. PA1 a: after executing parts 61, 62 and starting from an initial said first data block for each of 0.ltoreq.y.ltoreq.m successive first data blocks first forming a C1 code word and next a C2 code word; PA1 b1: for each data symbol of an ultimate said first data block, except for its last data symbol, forming an associated C2 code word; PA1 b2: subtracting all symbols of a block of s rows and q columns of symbols so formed from data symbols correspondingly positioned in the initial q said first blocks of symbols; PA1 c: after executing parts b1, b2 and starting from an ultimate said first data block for each of 0.ltoreq.z=m-y.ltoreq.m successive first data blocks first forming a C2 code word and next a C1 code word; PA1 d: after generating of parts a and c, generating a diamond shape containing p.times.q check symbols either through q C1 code words or through p C2 code words; PA1 e: after executing part b1 and completing the q columns comprising exclusively check symbols including those of part b1, adding all symbols of those q columns to symbols correspondingly positioned in the initial q symbol columns, and subsequently suppressing said block of q check columns. This is a straight-forward encoding procedure. PA1 a: after executing parts 61, 62 and starting from an initial said first data block for each of 0.ltoreq.y.ltoreq.m successive first data blocks first forming a C1 code word and next a C2 code word; PA1 b1: for each data symbol of an ultimate said first data block, except for its last data symbol, forming an associated C2 code word; PA1 b2: subtracting all symbols of a block of s rows and q columns of symbols so formed from data symbols correspondingly positioned in the initial q said first blocks of symbols; PA1 c: after executing parts b1, b2 and starting from an ultimate said first data block for each of 0.ltoreq.z=m-y.ltoreq.m successive first data blocks first forming a C2 code word and next a C1 code word; PA1 d: after generating of parts a and c, generating a diamond shape containing p.times.q check symbols either through q C1 code words or through p C2 code words; PA1 e: after executing part b1 and completing the q columns comprising exclusively check symbols including those of part b1, adding all symbols of those q columns to symbols correspondingly positioned in the initial q symbol columns, and subsequently suppressing said block of q check columns. PA1 a: after executing parts b1, b2 and starting from an initial said first data block for each of 0.ltoreq.y.ltoreq.m successive first data blocks first forming a C1 code word and next a C2 code word; PA1 b1: for each data symbol of an ultimate said first data block, except for its last data symbol, forming an associated C2 code word, while of each C2 code word so formed that has a final data symbol at contiguous row to an initial data symbol of a subsequent C2 code word, superposing the check symbols of the former C2 code word on the check symbols of the latter C2 code word, during their being generated; PA1 b2: subtracting all symbols of a block of s rows and q columns so formed from data symbols positioned on the same rows, in that from a data symbol in column j are subtracted, the check symbols in columns j+m, j+2m, etcetera, until all check symbols on the row in question have been subtracted one; PA1 c: after executing parts b1, b2 and starting from an ultimate said first data block for each of 0.ltoreq.z=m-y.ltoreq.m successive first data blocks first forming a C2 code word and next a C1 code word; PA1 d: after generating of parts a and c, generating a diamond shape containing p.times.q check symbols either through q C1 code words or through p C2 code words; PA1 e: after executing part b1, and completing the q columns comprising exclusively check symbols including those of part b1, adding all symbols of those q columns to symbols correspondingly positioned in the initial q symbol columns s, in the same manner and in point b2, and subsequently suppressing said block of q check columns. Further advantageous aspects are recited in dependent Claims.
The invention also relates to a device for executing the method. Such method and device, and in particular a decoding strategy therefor, have been disclosed in U.S. Pat. No. 4,477,903 (Ref I) to the present Assignee; a further particular decoding strategy has been disclosed in U.S. Pat. No. 4,683,572 (Ref.II), again to the same Assignee as the present application. In particular, all codes used for the present invention are linear codes, so that the sum of two code words is again a code word. This also allows for explicitly or implicitly converting a code word of a systematic code into a code word of a non-systematic code and vice versa. Now, the references relate to the error protection of the well-known Compact Disc system for recording and transmitting high-quality audio signals. Various extensions of that system have been based on the above error protection technology. In most cases the digital error protection is sufficient to exactly reproduce the original digital input signal, whilst in case of reproduction of an audio signal, a last recourse can be found by masking uncorrectable errors through some kind of interpolation on the audio signal itself. Although the above system has been widely and successfully commercialized, a need for higher performance has been felt, in respect of attainable data rate as well as in respect of increased robustness against errors to be offered by the code itself.